Variable speed, constant frequency electrical generating systems are used with variable speed prime movers to provide constant frequency electrical power to loads. A prime mover is connected with a variable speed generator. The variable frequency output of the generator is rectified and the DC powers a fixed frequency, solid state converter. A filter circuit smooths the output of the converter and traps switching harmonics.
Such electrical systems are particularly adapted for use with an aircraft engine where the generator is driven directly by the engine and the inverter has a 400 Hz output. It is also known to connect the AC to AC converter with another power source and to operate the variable frequency generator as a variable speed motor, driving the engine to starting speed in an engine start mode.